Method and device for session control in hybrid telecommunications network

ABSTRACT

Combinational networks may provide simultaneous connectivity over networks of different type between terminals. Communication sessions on different network types such as Circuit switched and Packet switched, belonging to the same user equipment can be correlated. In case a communication session on a circuit switched network is halted by a supplementary service e.g. at an event such as acceptance of Call Hold, a communication session on a correlated packet switched network should be halted as well. A user equipment that detects the event sends a halt message to the circuit switched network and a message to the packet switched network or a session state manager node. The session state manager node either forwards the halt-message to the packet switched network, or sends a halt-message to the packet switched network when the packet switched network does not notify that a halt has occurred.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/572,983, filed Feb. 5, 2008, now U.S. Pat. No. 7,881,287, which wasthe National Stage of International Application No. PCT/EP2005/008164,filed Jul. 28, 2005, which claims the benefit of U.S. ProvisionalApplication No. 60/60/592,492, filed Jul. 30, 2004, the disclosure ofwhich is incorporated herein by reference.

BACKGROUND

Fixed and especially mobile-networks, such as Global System for Mobilecommunications (GSM), General Packet Radio System (GPRS) or UniversalMobile Telecommunication System (UMTS) are constantly evolving. GSM/GPRSand UMTS networks today offer both Circuit Switched (CS) connectivityand Packet Switched (PS) connectivity. The PS end-to-end connectivitywith its capabilities for transmission of a wide range of data types maybe used for offering multimedia services such as image, music and videotransfer. The CS connectivity provides a link between two User Equipmentby means of one or more trusted network-nodes with a reliable anddefined Quality of Service (QoS) for e.g. voice traffic.

Combinational networks, where at least two links of at least twodifferent network types e.g. CS or PS, to one or more User Equipment areestablished, are capable of deploying CS and PS connectivitysimultaneously to a User Equipment, thereby enabling services, whichperform their activity by PS-communication sessions, and CScommunication sessions denoted as CS-calls. As this invention ispresented with application of an Internet Protocol Multimedia Subsystem(IMS) service, executed as a PS-communication session, the remainder ofthe invention denotes the PS_communication session as an IMS-session.

As to benefit from this form of service combination, User Equipmentcomprising one or more terminals are required that are capable ofhandling a CS-call and an IMS-session simultaneously. Multi Radio AccessBearer (RAB) terminals for UMTS and Dual Transfer Mode (DTM) terminalsfor GSM/GPRS networks will be available; these types of terminalsprovide support for simultaneous CS- and PS-connectivity.

Today, conversational voice cannot be delivered over PS radio bearers tothe end-user, due to e.g. insufficient capacity in the Radio AccessNetworks in operation and therefore existing CS bearers are used fordelivering conversational voice. In the future, it may be possible thata single PS bearer is used for conversational voice and multimedia.Nevertheless, DTM terminals already—, and possibly UMTS terminals in thefuture, deliver support for simultaneous CS- and PS-connectivity.

In order to give the end-user the look and feel of a single service,although the service may be composed of various CS-calls andIMS-sessions, deployed in the CS-network and the PS-networkrespectively, it is desirable to determine and deploy some form ofrelation between ongoing CS-calls or CS-calls that are being establishedand the ongoing IMS-session(s) or IMS-session(s) that are beingestablished. In the case that a CS-call is terminated or temporarilysuspended, the related IMS-session(s) should be terminated or suspendedas well as to provide the user the perception that both communicationsessions are strictly related to each other and provide a combinedservice.

A Call Hold event is an example of an event in a CS-network that mayhave effect in a simultaneous and correlated IMS-session at a UserEquipment. Call Hold is an example of a supplementary service in thecontext of Combinational Services, i.e. CS-services complemented withIMS, as defined by 3.rd Generation Partnership Project (3GPP), services,e.g. 3GPP specification TS 22.083, Call Waiting and Call Hold.

Although deploying telecommunication services such as voice, video anddata, over PS networks seems to be a realistic scenario for the nearfuture, some state of the art wireless networks e.g. GSM or UMTS, wouldnot be able to provide the required Quality of Service (QoS) for voicetraffic over a radio bearer of a PS network.

Combinational services, where the voice services are transported via thetraditional CS network and the video and data services via thePS-network provide a solution with respect to referred QoS.

The CS-networks provide a number of CS-services, e.g. supplementaryservices, for CS-calls. Currently developed IMS applications provide anumber of IMS-services for IMS-sessions available to an end-user via thePS-networks.

When an IMS service is applied within a combinational network, where theCS-call is transported via the CS-network and the IMS-sessions aretransported via the PS-network, there is no relation between the CS-callprovided by the CS-service and IMS session provided by the IMS-service,as the CS-call and the IMS-session are unrelated to each other due totransportation via different bearers.

3GPP specifications TS 22.083 [Call Waiting and Call Hold supplementaryservices, stage 1], TS 23.083 [Call Waiting and Call Hold supplementaryservices, stage 2], TS 24.080 [Mobile radio Layer 3 supplementaryservice specification; formats and coding], and TS 24.083 [Call Waitingand Call Hold supplementary services, stage 3] describe in detail a CSservice Call Waiting and Call Hold. The Call Hold service allows aserved mobile subscriber, who is provisioned with this SupplementaryService (SS), to interrupt communication on an existing active CS-calland subsequently, if desired, re-establish communication. A trafficchannel remains assigned to the mobile subscriber after thecommunication is interrupted to allow the origination or termination ofother calls [according to TS 22.083 stage 1].

When a Call Hold service is invoked, communication is interrupted on thetraffic channel and the traffic channel is released from the existingcall. The traffic channel is reserved for the served mobile subscriberinvoking the Call Hold service. The served mobile subscriber has onecall on hold at a time.

One traffic channel should be reserved for the served mobile subscriberas long as the subscriber has one call on hold and is currently notconnected to any other call, i.e. the network should not reserve morethan one traffic channel for a mobile station.

If the served mobile subscriber has a call on hold and is not connectedto an active call, the subscriber either: retrieves the held call, setsup another call, or disconnects the held call.

If the served mobile subscriber has a call on hold and is not connectedto an active call, the subscriber cannot receive a call, except whenusing the Call Waiting Supplementary Service.

If the served mobile subscriber is connected to an active call and hasanother call on hold, the subscriber either: alternates from one call tothe other, disconnects the active call, or disconnects the held call, ordisconnects both calls. If the served mobile subscriber is connected toan active call and has another call on hold, the subscriber cannotreceive a call. More detailed information is comprised in 3GPP TS22.083.

The Call Hold Supplementary Service has been specified within a CScontext. At the moment of specifying this Call Hold service, there wereno IMS services specified and therefore not included.

During the specification of IMS protocols and architecture it wasassumed that the voice component of multimedia services would be usingconversational PS-network bearers. Operator defined IMS-services may beexecuted by a Service Network. These IMS-services are not specified byIMS. Within IMS a number of primitives are specified which enable theService Network to execute IMS services. There is no existence of an“IMS-session Hold service” defined within the IMS specifications inanalogy towards the Call Hold service within the CS-domain.

Considering the deployment of a CS-domain service in combination with aPS-service such as IMS services, i.e. Combinational Services, a new areaof service interaction between CS-domain and IMS-domain based IMSservices occurred. For the combined Call Hold service, both theCS-domain service and the IMS services need to be suspended and theCS-domain- and IMS connectivity interrupted, when a Call Hold event hasoccurred within the CS-network.

An additional issue is the influence of the security principles withinthe network. In general a User Equipment is not regarded as a trustedentity within the network, although it is responsible for the initiationof a number of relevant network procedures, such as Call Hold.Therefore, a validation mechanism needs to be available that complementsthe User Equipment as to compensate the “untrusted” nature of the UserEquipment.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method ofcontrolling communication sessions present in a combinational networkcomprising two or more networks of at least two different network typesbeing a CS-network and at least one PS-network, on an event occurringwithin a CS-network where said communication sessions being a CS-call atthe CS network and an IMS-session at the PS-network are related to aparty having a User Equipment (UE) deploying said sessions at thenetworks of different network type.

The method provides control of the CS-call and the one or moreIMS-sessions with Supplementary CS-domain services such as Call Hold,which CS-domain service is cooperating with an IMS service based at theIMS-domain.

It is a further object of the present invention to provide an UE and anetwork device, which is arranged for performing said control of thecommunication sessions according to the method provided.

These objects are achieved by the present invention by means of a methodof providing session control within a telecommunications systemcomprising at least two networks of at least two different networktypes, where the networks are connected to a UE and a network entity,both having network connections to at least two of the networks, whereinthe method provides for detecting an event, such as an accepted CallHold, at the CS-network that requires a related IMS-session to becontrolled, composing and providing a first message to the CS-network asto control the CS-call and composing and providing a second message tothe PS-network as to control the one or more IMS-sessions. A deviceperforming the detecting, the composing and the providing steps isprovided as well.

The method according to the present invention is based on the insightthat the UE that detects the event such as the accepted Call Hold, sendsthe first message to the CS-network and sends the second message to thePS-network, and expects the appropriate action from the CS-network andthe PS-network. The appropriate action is to be applied on an ongoingcorrelated communication IMS-session at the PS-network. In a firstsolution a session state manager node receives a notifications from theCS-network and the PS-network that the action is performed. In case thenotification of the PS-network does not arrive (in time) the sessionstate manager node sends the PS-network the second message. In a secondsolution the second message is sent by the UE to the PS-network via thesession state manager node.

The method provides that the session state manager node is triggered tocontrol a IMS-domain based service in an appropriate predetermined way,such as interrupt, resume or terminate or to forward

The method provides a network entity that keeps session stateinformation within the network such that applications on a service layerare provided with means to interrogate the session state of an ongoingcombinational service.

Deployment of the invention as presented enables that e.g. theinvocation of a Call Hold service within the CS- and/or IMS-networkshall trigger a session state update towards the mentioned session statemanager node containing the session state information.

These and other embodiments according to the present invention are nowillustrated in more detail with reference to the enclosed drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 presents a schematic diagram of a combinational network with twoUE connected to the combinational network.

FIG. 2A presents a time sequence diagram of the message flows between anUE, a CS-domain network session node, an IMS-domain network session nodeand a session state manager node where the UE messages the IMS-domainnetwork session node for a Call Hold.

FIG. 2B presents a time sequence diagram of the message flows between anUE, a CS-domain network session node, an IMS-domain network session nodeand a session state manager node where the UE messages the IMS-domainnetwork session node for a Call Hold via the session state manager node

FIG. 2C presents a time sequence diagram of the message flows between anUE, a CS-domain network session node, an IMS-domain network session nodeand a session state manager node where the UE messages the CS-domainnetwork session node for a Call Hold, and where this CS-domain networksession node messages the session state manager that a call isestablished between two parties, denoted as an A-party and a C-party,intentionally to have the session state manager node request theIMS-domain network session node to hold the IMS-session.

FIG. 3 presents a schematic diagram of a part of a communication devicesuch as a UE.

DETAILED DESCRIPTION

Without restrictions to the scope of the invention, in order to providea thorough understanding of the present invention, the invention ispresented against the background and within the scope of the currentimplementation of mobile communication system deployed in acombinational network environment. However, the present invention may bedeployed in any communication system comprising combinational networks.

Suppose that two users, A-party and B-party have communication sessionsongoing. Said communication sessions between the A-party and the B-partyconsist of a CS-call provided by the CS-network and an IMS-sessionprovided by the PS-network, both communication sessions regarded as“communication components”. UE used by the A-party and UE used by theB-party shall allow for CS and PS communications sessionssimultaneously, which is referred to as dual-mode communication. Thesaid dual-mode communication capability may be present in a singledevice or in a multitude of devices, such as a split UE arrangementwhere said dual-mode UE comprises e.g. a mobile phone and a PersonalComputer (PC).

Messages exchanged between said parties to establish communicationand/or messages exchanged during communication can be intercepted andmodified by a “Service Network” comprising network entities havingconnections to networks of at least two different network types withinthe combinational network.

FIG. 1 illustrates schematically a network with several network entities1, 2, 5, 8, 34 and a combinational network 10 comprising severalnetworks of at least two different network types 11, 12, 13, with afirst UE 1 and a second UE 2 connected to all or at least two of thenetworks 11, 12, 13.

As to provide a physical connection to the networks 11, 12, 13, the UE1, 2 has network interfaces each associated with a network address,towards said networks 11, 12, 13.

For the explanation of the invention, it is arbitrarily assumed thatnetwork 11 is a network of a CS-network type, and networks 12 and 13 arenetworks of a PS-network type. The combination of the CS-network 11 withCS-services is regarded as a CS-domain, and the combination of thePS-network 12, 13 with IMS-services is regarded as an IMS-domain.

In the description below, it will be explained how an event during aCS-call occurring within the CS-network 11 results in an appropriateaction at a correlated IMS-session within the PS-network 12, 13. Withoutany restriction to the scope of the invention a Call Hold event will beused to elucidate the method proposed by the invention.

The invention addresses three closely related solutions to a problem ofcontrolling correlated communication sessions in the combinationalnetwork 10 by means of introduction of a network entity named “sessionstate manager” node 5.

The solutions described assume that the A-party UE 1 and the B-party UE2 have an ongoing CS-call connectivity to each other via the CS-network11 and a related ongoing IMS session to each other via the PS-network12, 13. The explanation below describes a single ongoing IMS-session atthe PS-network 12, 13, however a multiple of simultaneous IMS-sessionsat the same or multiple PS-networks 12, 13 is deployed in the same wayas a single IMS-session provided by the PS-network 12, 13.

Network entity 34, implemented as a content server, is connected to thenetworks 11, 12, 13 and may just as UE 2 have related simultaneouscommunication sessions over the networks 11, 12, 13 with UE 1. Althoughthe invention is explained in the case that UE 1 and UE 2 havecorrelated communication sessions, the case that UE 1 has correlatedcommunication sessions to content server 34 would be included by theinvention as well.

FIG. 1 also shows network entities comprised in combinational network10, such as network session nodes 6, 7.

A CS-domain network session node 7 is comprised in the CS-domain, and isarranged to receive messages from the UE 1, 2 or network entity 34.

This CS-domain network session node 7 is arranged to have the CS-network11 execute an event such as a Call Hold for the CS-connection betweenthe A-party's UE 1 and the B-party's UE 2 and a Call Establishment forthe A-party's UE 1 and the C-party's UE. The CS-domain network sessionnode 7 is arranged to notify—or to provide an event message to—a sessionstate manager 5, as to enable the session state manager node 5 toperform an appropriate action towards the IMS-domain. The action couldbe e.g. an interruption or termination of an ongoing IMS-session at theIMS-domain in response to the event occurring in the CS-domain.

Furthermore the CS-domain network session node 7 is arranged to generatean event such as a Call Hold, which event is to be detected by the UE 1,2 or content server 34.

The CS-domain network session node 7 may also be arranged to receive amessage, based on an event generated by another network node.

An IMS-domain network session node 6 is comprised in the IMS-domain, andis arranged to receive messages from the UE 1, 2 or network entity 34.

This IMS-domain network session node 6 is arranged to interpret saidmessage and accordingly interrupt or terminate an ongoing IMS-sessionbetween the A-party's UE and the B-party's UE or the content server 34on request of the UE 1, 2, the content server 34 or the session statemanager 5. Apart from interrupting or terminating the ongoingIMS-session, the IMS-domain network session node 6 suspends, resumes,delays, accelerates or increases/decreases a bandwidth of a bearer ofthe PS-network.

The IMS-domain network session node 6 is arranged to notify—or toprovide an event message to—a session state manager 5, as to inform thesession state manager node 5 on the actual state of the IMS session(s).

Furthermore the IMS-domain network session node 6 is arranged togenerate an event such as an IMS-session “Hold”, which event is to bedetected by the UE 1, 2 or content server 34.

The IMS-domain network session node 6 may also be arranged to receive amessage, based on an event generated by another network node.

The message received by the IMS-domain network session node 6 maycomprise a timestamp and the IMS-domain network session node 6 isarranged to synchronise the terminating- or the suspending-action withthe timestamp.

The IMS-domain network session node 6 has the capability to defer theexecution of a suspension or a termination of the IMS-session inprogress until the IMS-session is completed. The defer action takesplace on receiving the message. The IMS-domain network session node 6may be implemented as an IMS-server.

An external network node 8, located outside the networks 11, 12, 13having connections to the networks 11, 12, may also generate the eventthat will, when detected, effect the resulting actions by the CS-domainor IMS-domain network session nodes 6, 7.

The session state manager node 5 is arranged to:

receive notifications from the CS-domain network session node 7 and theIMS-domain network session node 6 that a “Hold” in the respectiveCS-call or IMS-session has occurred.

receive an IMS-session Hold message or a Call Hold event message fromthe UE 1, 2 or content server 34.

receive a Call Hold event message from the A-party's UE 1, the B-party'sUE 2 or the content server 34.

send a Call Hold event message or IMS-session Hold message to theIMS-domain network session node 6.

Keep CS-call- and IMS-session-state information within the network suchthat applications on a service layer are provided with means tointerrogate the session state of an ongoing combinational service.

Furthermore the session state manager node may generate the event.

The session state manager has knowledge of related CS-call and IMSsessions and has the ability to check on a correlation for said CS-callsand PS-sessions according to prior art methods.

A first solution is based on sending of an IMS-session Hold message bythe UE 1, 2, towards to the IMS-domain network session node 6. ThePS-network 12, 13 will inform a session state manager node 5 by means ofa PS-network notification that an IMS session between the A-party UE 1and the B-party UE 2 has been put on hold. In addition to the mentionedPS-network notification, the session state manager node 5 will also beupdated by a notification from the CS-network 11, indicating that the CSconnection between the A-party UE 1 and the B-party UE 2 has been put onhold.

With reference to FIG. 2A the first solution is explained. Suppose thatthe A-party's UE 1 receives a terminating call attempt from a C-party'sUE, while the A-party's UE 1 has a correlated ongoing CS-call and anongoing IMS-session towards the B-party's UE 2. The A-party decides toaccept the call from the C-party and puts the CS-call with the B-partyon hold. According to prior art methods the A-party's UE 1 sends a CallHold message 211 to the CS-domain network session node 7 as to have theCS-network execute a Call Hold for the CS connection between theA-party's UE 1 and the B-party's UE 2. The invention provides in thisfirst solution that the A-party's UE sends as well an IMS-session Holdmessage 212 to the IMS-domain network session node 6 to put theIMS-session between the A-party's UE 1 and the B-party's UE 2 on hold.Both the CS-domain network session node 7 and the IMS-domain networksession node 6 notify 213, 214 the session state manager node 5 thattheir respective sessions between the A-party's UE 1 and the B-party'sUE 2 have been set an hold.

This first solution is based on the sending of an IMS-session Holdmessage 212 by means of the UE 1, 2 to IMS-domain network session node6. The PS-network 12, 13 will notify 214 a session state manager node 5that the IMS session between the A-party's UE 1 and the B-party's UE 2has been put on hold. In addition to the mentioned IMS networknotification, the session state manager node 5 will also be updated by anotification 213 from the CS-network 11, indicating that the CSconnection between the A-party UE 1 and the B-party UE 2 has been put onhold. In this way session state manager node 5 has a complete overviewof the actual state of the sessions at the networks 11, 12, 13.

In the case that the UE 1 did not for any reason sent the IMS-sessionHold message 212 towards the IMS-domain network session node 6, suchthat a notification that the IMS-session is halted is not received in atime interval .DELTA.t after having received a notification 213 that theCS session has been set on hold, the session state manager notifies 215the IMS-domain network session node 6 to halt the ongoing IMS-session.

As an extension to this first solution, the IMS-domain network sessionnode 6 will, after receiving the IMS-session Hold message 212 from theA-party's UE 1, instead of suspending the ongoing IMS sessionimmediately, either:

a) synchronise the IMS-session Hold action with a timestamp comprised inthe second message. b) maintain the ongoing IMS-session until theongoing session is completed.

With reference to FIG. 2B a second solution is explained. Suppose thatthe A-party's UE 1 receives a terminating call attempt from a C-party'sUE, while the A-party's UE 1 has a correlated ongoing CS-call with anongoing IMS-session towards a B-party's UE 2. The A-party decides toaccept the call from the C-party and puts the CS-call with the B-partyon hold. According to prior art methods the A-party's UE 1 sends a CallHold message 221 to the CS-domain network session node 7 as to have theCS-network execute a Call Hold for the CS connection between theA-party's UE 1 and the B-party's UE 2. The invention provides in thissecond solution that the A-party's UE 1 sends a Call Hold event message222 towards the session state manager node 5 as to indicate that theCS-call between the A-party's UE 1 and the B-party's UE 2 has been puton hold. By sending this Call Hold event message 222, the UE 1 expectsthat the session state manager node 5 performs a hold of theIMS-session.

The A-party's UE 1 sends this Call Hold event message 222 via either theCS-network 11 or the PS network 12, 13, as the UE 1 is connected to (atleast) both network types of the networks (11, 12, 13).

In response to the received Call Hold event message from the UE 1, thesession state manager node 5 will send a Call Hold event message 223 tothe IMS-domain network session node 6 as Do indicate that the CS-callbetween the A-party's UE 1 and the B-party's UE 2 has been put on hold.Subsequently the IMS-domain network session node 6 suspends the IMSsession between the A-party's UE 1 and the B-party's UE 2.

In this second solution the UE 1, 2 has a connection via CS-network 11or via PS-network 12, 13 towards the session state manager node 5 andinforms 222 the session state manager node 5 when it initiates a CallHold request to the CS-domain. The session state manager node 5 updatesits session state information and notifies 223 the IMS-domain to breakthe IMS connectivity between the A-party's UE 1 and the B-party's UE 2.

As an extension to this second solution, the IMS-domain network sessionnode 6 will, after receiving the message 223 from the session statemanager node 5, instead of suspending the ongoing IMS sessionimmediately, either:

a) synchronise the IMS-session Hold action with a timestamp comprised inthe second message. b) maintain the ongoing IMS-session until theongoing session is completed.

With reference to FIG. 2C a third solution is explained as analternative to the cases where the UE 1 is sending a first and a secondCS/IMS Hold message to the CS-domain network session node 7 and theIMS-domain network session node 6 respectively. In this alternative theUE is sending only one message.

Suppose that the A-party's UE 1 receives a terminating call attempt froma C-party's UE, while the A-party's UE 1 has a correlated ongoingCS-call with an ongoing IMS-session towards a B-party's UE 2. TheA-party decides to accept the CS-call from the C-party and puts theCS-call with the B-party on hold.

According to prior art methods the A-party's UE 1 sends a call holdmessage 231 to a CS-domain network session node 7 as to have theCS-network execute a Call Hold for the CS connection between theA-party's UE 1 and the B-party's UE 2. The invention provides in thisthird solution that the CS-domain network session node 7 sends aCS-domain event message 232 to the session state manager node 5 as toindicate an accepted call from the C-party by the A-party's UE 1.Subsequently the session state manager node 5 informs the IMS-domainabout the CS-domain Call Hold by sending an IMS notification 233containing an instruction that the IMS session between the A-party's UE1 and the B-party's UE 2 shall be suspended. The IMS-domain networksession node 6 suspends the IMS-session after the message 233 has beenreceived from the session state manager node 5. This suspension of theIMS-session is optionally executed such that the actual suspension isdelayed until the IMS-session in progress has ended, or that theinterruption is synchronised with a timestamp provided by thenotification of the session state manager 5.

In this third solution the CS-domain network session node 7 notifies 232the session state manager node 5 that a connection has been establishedbetween the A-party's UE 1 and a C-party's UE. The session state managernode 5 realises that the A-party's UE 1 was already engaged within acombinational session with the B-party's UE 2, and will notify thePS-network 12, 13 that the PS connectivity between the A-party's UE 1and the B-party's UE 2 needs to be interrupted.

As an extension to this third solution, the IMS-domain network sessionnode 6 will, after receiving the message 233 from the session statemanager node 5, instead of suspending the ongoing IMS sessionimmediately, either:

a) synchronise the IMS-session Hold action with a timestamp comprised inthe second message. b) maintain the ongoing IMS-session until theongoing session is completed.

With reference to FIG. 3, representing schematically a part of acommunication device such as a UE, the UE 1, 2 will be explained.

The UE 1, 2 comprises an Input Output (I/O) unit 101 connected to thenetworks 11, 12, 13, by means of interfaces 1A, 1B, 1C, each with anetwork address. The event whereupon the Call Hold and IMS-session Holdare, might be generated by the UE 1, 2 or be received by the I/O unit101. The I/O unit 101 may also receive the event from another networkentity 2, 5, 8, 34, and sends the first- and second-message via theinterfaces 1A, 1B, 1C. The UE 1, 2 comprises a memory unit 103 that isarranged for storing the event and the messages.

The processing unit 102 with application program storage 102A for anapplication programme, is arranged for detecting the event, composingthe first- and second-message, based on the event, according topredetermined rules and parameters, such as time of the day or asubscriber profile. The application programme is an IMS application.

The UE 1, 2 is implemented as a terminal such as a Dual Transfer Mode(DTM) terminal, a Global System for Mobile communications-General PacketRadio System (GSM-GPRS) terminal or a Universal Mobile TelecommunicationSystem Multi Radio Access Bearer (UMTS Multi-RAB) terminal.

If the UE 1, 2 is implemented as a split terminal environment, the CSconnection is accomplished by terminals such as a telephone, a headset,a Global System for Mobile communications (GSM) terminal, an AdvancedMobile Phone System (AMPS), a Digital AMPS (D-AMPS) terminal, DigitalEnhanced Cordless Telephony (DECT) terminal, Bluetooth terminal or aUniversal Mobile Telecommunication System (UMTS) terminal. In the splitterminal the PS connectivity is accomplished by a terminals such as avideo terminal, a Personal Computer (PC) or workstation. Input means 104of UE 1 provides a way to initialise the event at the UE 1,2.

Implementation of the invention is provided by deploying prior artnetwork entities, such as a Mobile Switching Center (MSC) as CS-domainnetwork session node 7 and a Session Initiation Protocol-applicationserver (SIP-AS) as IMS-domain network session node 6.

The messages types and network addresses used between the UE 1, 2, 34,the network session nodes 6, 7 and the session state manager node 5, areprior art messages types and addresses, depending on the network type.

The session state manager node 5 reflects the status of a multimediasession within the combinational network. The CS-call and the PS-sessionare correlated. In case the session manager node 5 would need to checkif a correlation exists, a method disclosed at co-pending applicationU.S. 60/592,426 may be used. This co-pending application shows a methodwhere a number of logical databases is introduced which contain actualdata on relations between network addresses and communication sessions,where a correlation check is deployed by a correlation node. The checkconsists of a number of queries towards said databases or to othernetwork entities, yielding whether the communication session is to beregarded as combinational. The correlation node, which establishes thatthe communication sessions are present, determines a correlation betweenthe communication sessions and provides the determined correlation to asubsystem. The establishing of the presence of the communicationsessions comprises the steps of retrieving the network addresses of thefirst User Equipment and the network entity via a CS-network and via aPS-network, and verifying the presence of the communication sessions onboth network types.

The session state manager node 5 reflects the status of a multimediasession within the combinational network where network addresses ofCS-network type and PS-network type of the UE 1, 2 are available. Incase the session state manager node 5 needs to retrieve a PS-networktype network address of the UE 1,2 a method disclosed at co-pendingapplication U.S. 60/592,427 may be used. This co-pending applicationshows a method and device for retrieving the PS address of a circuitswitched call partner, where a retrieval for a PS network address isinitialised by means of a CS protocol via a CS-network. The addressretrieval request is directed to the CS call partner or a networkservice that accomplishes the network address request. The request isreceived by the CS-call partner's User Equipment and the PS-networkaddress is looked up and sent back to the requesting User Equipment

Combinational Services are currently being standardised by 3GPP. Thereuse of CS infrastructure allows for stepwise introduction of IMSservices without the need for major investment by the operator. Anotheraspect will be the introduction of new advanced Multimedia services tothe call and therefore introducing an, enriched user experience of thebasic communication needs (i.e. making calls).

A number of services are quite commonly used by users in the context ofvoice calls, e.g. supplementary services. However, in the context ofenriched voice services the handling of the supplementary services isbecoming an issue. The present invention provides a solution byintroducing the session state manager node 5 in cooperation with thenetwork session nodes 6, 7, for controlling sessions in the context ofcombinational services once the supplementary service such as a CallHold is invoked.

The invention as presented provides a control method for a relatedCS-call and IMS-session in a combinational context. By deployment of theinvention, invocations of CS-domain supplementary services are able toinfluence the associated IMS services and may e.g. temporarily suspendthe IMS connectivity in a convenient and efficient way.

As in each solution presented, the session manager node 5 has a checking(solution 1) or an active (solution 2, 3) role, and hence is involvedand has influence in a process of controlling the IMS-session. Thissession manager node 5 is regarded as a trusted network entity and ispotentially capable to detect and correct any action of the UE 1, 2 thatinitialised the event. The inclusion of the trusted session manager node5 according to the invention allows the use of an UE that is regarded asuntrusted.

1.-30. (canceled)
 31. A method for providing session control within atelecommunications system comprising at least two networks of at leasttwo different network types, where the networks are connecting at leasta first user equipment and a network entity, where the first userequipment and the network entity have network connections to at leasttwo of the networks of different network type the method comprising thesteps of: detecting an event within a first communication session, saidcommunication session being present on the network of a first networktype, wherein the event is a Call Hold event or a termination event;composing a first message based on said event; providing the firstmessage to a network node comprised within the network of the firstnetwork type so as to control the first communication session, composinga second message based on said event, providing the second message to anetwork node, so as to control a second communication session, beingpresent on the network of a second network type; wherein the first andthe second communication session are present simultaneously on thenetworks of the different network types and where the first and thesecond communication sessions are combinational.
 32. The methodaccording to claim 32, wherein a holding or terminating action at theIMS server, based on the event and the second message associated withthe event, is synchronized with a timestamp comprised in the secondmessage.